docs: def _get(self, i):
          """
          Retrieve data for the ith file in the dataset.
          """
          with open(os.path.join(self.path, self.elem, self.files[i]), 'r') as f:
              # JSTOR hasn't always produced valid XML.
              contents = re.sub('(&)(?!amp;)', lambda match: '&amp;', f.read())
              root = ET.fromstring(contents)
          doi = root.attrib['id']
  
          if self.K:  # Keys only.
              return doi
  
          grams = []
          for gram in root.findall(self.elem_xml):
              text = unidecode(unicode(gram.text.strip()))
              if ( not self.ignore_hash or '#' not in list(text) ):
                  c = ( text, number(gram.attrib['weight']) )
                  grams.append(c)
  
          if self.V:  # Values only.
              return grams
  
          return doi, grams